Automatic device for discrete compensation of the metallostatic pressure in machines for casting with gas pressure

ABSTRACT

An automatic system for discretely adjusting the metallostatic pressure of a metal-casting machine operating under a pressure differential receives an input to its ring counter from the casting unit representing the number of casting cycles. The output of the ring counter is applied to the shift register which, in response to the count, operates an output circuit to provide a control signal adjusting the differential pressure in accordance with a number of castings produced.

United States Patent 91 Nikolov et al. I

[ June 4,1974

[22] Filed:

[ AUTOMATIC DEVICE FOR DISCRETE COMPENSATION OF THE METALLOSTATICPRESSURE IN MACHINES FOR CASTING WITH GAS PRESSURE [75] Inventors: IvanDimov Nikolov; Gueorgui Nikolov Rasheev; Ferdo Atanasov Sivov; NikolaiYonkov Nikolov; Chavdar Asenov Hristov, all of Sofia, Bulgaria a [73]Assignee: Institut Po Metaloznamie I Technologia Na Metalite, Sofia,Bulgaria j l Apr. 26, 1972 [21 Appl. No.: 247,716

[30] Foreign Application Priority Data Y Apr. 29, I97] Bulgaria 1 7444-[52 u.s.c|. l37/624.ll

METAL-FEED INPUT PULSE FORM INVERTER AND GATE PULSE OR GATES [51] Int.Cl. Fl6k 31/00 [58] Field of Seanch l37/624.ll

[56] References Cited UNITED STATES PATENTS 3.74l,246 6/l973 Braytenbahl37/624.l 1

Primary Examiner--Henry T. Klinksiek Attorney, Agent, or Firm-Karl F.Ross; Herbert Dubno 571 ABSTRACT An automatic system for discretelyadjusting the metallostatic pressure of a metal-casting machineoperating under a pressure differential receives an input to its ringcounter from the casting unit representing the number of casting cycles.The output of the ring counter is applied to the shift register which,in response to the count, operates an output circuit to provide acontrol signal adjusting the differential pressure in accordance with anumber of castings produced.

1 Claim, 3' Drawing Figures mvznren a6 GATE owner 49 as 1 a0 INVERTERGATES PATENTEUJUN 41974 SMEIIIIFZ CASTING INPUT /5- ll MAXIMUM PRESSUREPRESETTABLE RING COUNTER (SHIFT REGISTER I Fig.1

OUTPUT DIFFERENTIAL CCT PRESSURE MINIMUM PRESSURE The present inventionrelates to a system for the establishment of discrete pressuredifferentials in apparatus for the casting of metals under gas pressureso as to vary in increments the differential pressure effecting thecasting with the decreasing level of metal in the crucible.

in the casting of molten metals under differential pressure, metal canbe forced'from a crucible at a high pressure through a tube into a moldin a chamber at relatively low pressure so that the molten metal isdisplaced at least in part under the pressure differential. Themetallostatic pressure, of course, depends upon the head of molten metalwhich must be overcome to displace the metal through the tube. As themolten metal in the crucibleis discharged,'i.e. atlevel drops, with theproduction of castings, the differential pressure applied to the systemmust be varied so as to maintain casting uniformity.

This compensation of the pressure differential can be carried out byhand and a pneumatic fluidics transducer for this purpose has beendescribed in Bulgarian Pat. No. 14,499 filed Oct. 17, 1969. In thissystem the differential pressure may be set at either of two levelsmanually by setting two systems of pneumatic nozzles which establishrespective differential pressures. It is not possible with this systemto automatically vary the differential as the level f molten metaldecreases in the crucible so that, after a certain number of castingcycles, the product is unsatisfactory and must be scrapped. i it istheobject'of the invention to provide a system for discretely adjustingthe pressure differential in accordance with the variation of the levelof molten metal in the crucible and thereby avoid the disadvantages ofthe earlier system. i I

The system of the present invention provides for automatic switchoverfrom one operating (pressurecontrolling) nozzle to another in successioninaccordance with a manometer reading and in response to variation inthe level of molten metal in the crucible (determined by counting thenumber of castings made).

The system has been found to permit full utilization of the metal in thecrucible, casting at a constant pressure as seen in the mold andregulation over a wide range of the initial value of the differentialpressure. The system thus can be used in avariety of machines forcasting metals under pressure, independently of the size of the crucibleor the type of metal cast.

Another advantage is that the number of nozzle sets(differential-pressure increments) is not limited so that a largevariety of differential pressures may be employed and the rate at whichthe differential pressure increments are changed can be varied.

The invention is best described in conjunction with the drawing inwhich:

FIG. 1 is a block diagram illustrating the basic elements of the presentinvention;

FIG. 2 is a circuit diagram showing the various logic elements employedin the block diagram of FIG. 1; and

FIG. 3 is a diagram illustrating the manometer and the nozzlearrangements used therewith.

As illustrated in FIG; 1, the system according to the present inventionconsists basically of a presettable ring counter (A) receiving an input15 upon the completion of each casting operation, the input thereforerepresenting the incremental decrease in the level of the metal in thecrucible represented by each single casting'. The output of this ringcounter is applied to a shift register B generating an enabling signalwhen the count reaches' a predetermined level to signal a differentialpressure change to the output circuit C. The signal is supplied as willbe apparent from FIG. 2, to logic elements insuring stepped differentialpressures as established by selective nozzles of a fluidics or bafflenozzle control system for the differential pressure which is applied tothe casting machine in the manner described,

in the aforementioned patent.

Referring now to FIG. 3 it will be apparent that the manometer has adial face over which is shiftable the temperature-indicating pointer 16which carries a partition or movable vane or baffle 59 adapted topassbetween juxtaposed sets of nozzles which are effective to generate asignal as described at page 419 of SERVO- MECHANISM PRACTICE, McGrawHill Book Co., Znd Edition, 1960. The signal from the shift register iscombined with the fluid pressure signal from the nozzle s to generate anoutput which is obtained at 57 and represents the set differentialpressure. Outputs 56 and 58 represent, respectively, the preset maximumpressure and the preset minimum pressure corresponding to nozzle sets 43and 44 respectively.

The ring counter A (FIG. 2)'basically comprises a pulse former or shaperl which converts the input signal 15 into an electrical pulse ofwell-definedwaveform which is applied to one input of an AND gate 5feeding a digital pulse counter or summer 7. The AND gate 5 passes thesignal 15 when it receives a clock signal from a trigger or clock-pulsegenerator 11 which may be of the multivibrator type. Hence the pulsecounter 7 gives an output signal only when the number of input pulsesfrom the AND gate exceeds the digit preset at the counter7.

The output signal is applied to an inverter 8 which supplies both inputsof an OR gate 9 to deliver asignal to the trigger circuit 11. The outputsignal, representing a count beyond the number preset in counter 7, isapplied through the pulse shaper 12 to an AND gate 16 at the input tothe shift register B. Simultaneously, the pulse is applied to aninverter 14 and a pulse shaper 13 which feeds one input of the OR gate10. This operates the trigger 11 to enable the AND gate 5 for the nextcount. In addition,,the signal from pulse shaper 12 is applied to atwo-input OR gate 6 to reset the counter 7 and renders it effective forthe next counting cycle.

As indicated, when the preset count at counter 7 is exceeded, an inputis applied to the AND gate 16 of the shift register B. When the AND gate16 is enabled by v r 3 an input from the last OR gate 26 as will bedescribed in greater detail hereinafter, it delivers a signal to thesingle input trigger l7 (flip-flop) which, in accordance with shiftregister principles, delivers a signal after an initial change of statewhich is applied through the pulse shaper to the next trigger orflip-flop 18. The latter likewise delivers its signal following a changeof state to the trigger or flip-flop 19. Each of the triggers 17 19 maybe reset either by the pushbutton 2 or by the pressure signal H via theOR gate 3.

in accordance with shift register principles the application of fivesuccessive pulses by the AND gate 16 to the flip-flop i7 19 will resultin five different states of the flip-flops and hence differentvariations of output signals to an array of four three-input OR gates 2226. As a consequence, a zero signal (null) is applied to only one of theprohibitive gates 28 '32 (AND gates having a negation or inversioninput). Thus only one output renders the associated set of nozzles 37 33effective. This set of nozzles is thereby rendered effective andcooperates with the movable vane in the manner described inSERVOMECHANISM PRACTICE cited earlier to control the pressure. Theoutput signal of the operating nozzle is fed through the OR-NOT gate 3842 and to a five input OR gate 61 and an inverter 55 for supplying theother control circuits of the machine with a signal 57 representing thedifferential pressure.

A common feed for all of the nozzles is provided at H and an indicator48 54 is provided with each nozzle to permit visual indication of theeffective set of nozzles or pressure. A switch 55 applies a signalthrough, the AND gate 27 to the nozzle 28 to override, if desired, theautomatic compensation system. The pneumatic nozzles 33 37, 43 and 44can be adjustable in a slot of the dial of the manometer.

We claim:

l. A system for controlling in discrete increments the differentialpressure of a casting apparatus operating under a pressure differentialin response to changes in the level of molten metal in a crucible, saidsystem comprising:

a ring counter receiving a sequence of input pulses representingsuccessive castings by said apparatus and corresponding reduction in thelevel of molten metal in said crucible producing anoutput pulse upon thedetection of an input pulse following a predetermined number of inputpulses of said sequence; I 1 e a pulse shaping device receiving saidoutput pulse and an AND gate responsive to the shaped output pulse forproducing a stepping pulse;

a shift register comprising a plurality of sequentially connectedbistable triggers having output states corresponding to the number oftrigger pulses produced by said AND gate, said triggers each having twooutputs;

a plurality of multiple input OR gates each having a respective inputconnected to an output of each of said triggers, said'OR gates eachhaving an output, the output of the OR gate corresponding to the finalstate of said shift register being connected to the input of said ANDgate;

means for selectively energizing respective fluidicdifferential-pressure controllers from each output of the respective ORgate;

' means for producing an output signal representing the differentialpressure selected by the respective OR gate;

a further AND gate receiving an output from-one of said OR gates andinterposed between said one of said OR gates and the respective fluidicpressure differential controller; and

switch means connected to a second input of said further AND gate forterminating automatic setting of the differential pressure.

1. A system for controlling in discrete increments the differentialpressure of a casting apparatus operating under a pressure differentialin response to changes in the level of molten metal in a crucible, saidsystem comprising: a ring counter receiving a sequence of input pulsesrepresenting successive castings by said apparatus and correspondingreduction in the level of molten metal in said crucible producing anoutput pulse upon the detection of an input pulse following apredetermined number of input pulses of said sequence; a pulse shapingdevice receiving said output pulse and an AND gate responsive to theshaped output pulse for producing a stepping pulse; a shift registercomprising a plurality of sequentially connected bistable triggershaving output states corresponding to the number of trigger pulsesproduced by said AND gate, said triggers each having two outputs; aplurality of multiple input OR gates each having a respective inputconnected to an output of each of said triggers, said OR gates eachhaving an output, the output of the OR gate corresponding to the finalstate of said shift register being connected to the input of said ANDgate; means for selectively energizing respective fluidicdifferential-pressure controllers from each output of the respective ORgate; means for producing an output signal representing the differentialpressure selected by the respective OR gate; a further AND gatereceiving an output from one of said OR gates and interposed betweensaid one of said OR gates and the respective fluidic pressuredifferential controller; and switch means connected to a second input ofsaid further AND gate for terminating automatic setting of thedifferential pressure.